Boil the rice in water for 15-20 minutes, then drain and let cool.
Separate the eggs and beat the egg whites into snow. Melt the butter, stir in the sugar, egg yolk, salt and cinnamon until frothy. Mix carefully with the quark, rice and egg whites.
Pour the mixture into a greased casserole dish and bake at 180 ° C top / bottom heat for 1 hour.
Serve immediately, with a glass of cherries or whatever you like.